selectall_arrayref returns an array ref of rows, and each row is an array ref again, so it looks like this:

my $doclist = [['prod1'], ['prod2']];
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You can remove remove these easily:

my @flat_doclist = map $_->[0], @$doclist;

# and then later:
print scrolling_list(-name => 'cboProj',
                     -values => \@flat_doclist);
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See also: perllol, perldata, perlreftut.